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Hi guys,imback forgot to log out, considering that he mentioned
Flaking in the tower. My guess would be that the chiller is logg
Ing "low end surges due to not enough load". It's pretty heard to hear
In a loud mech. Room. Sounds like low grumbling, can sometime
Be mistaken for a bearing problem. I worked for York awhile
Back, have heard this in winter mainly. What do you guys think?

...considering that he mentioned
Flaking in the tower. My guess would be that the chiller is logg
Ing "low end surges due to not enough load".

I think you are confusing "stall" with surge. The tower problems would not contribute to the low load conditions of which you speak. The rumbling one experiences in low load conditions is usually not a surge, but rather a "stall" condition. The two are very different conditions. Surging occurs when actual head exceeds design head. A stall condition occurs when then refrigerant gas recirculates within the impeller and is unable to be pushed into the volute. After York came out with the YK series there were cases of stall that needed to be addressed. Stall can cause damage to the compressor/chiller as well. What York developed was the VGD or variable geometry diffuser. This diffuser closes the gap in the discharge wall to allow the refrigerant to get through the volute and into the condenser.

Have several yt machines with new drives. VERY sensitive. Hard to get to back off hertz unless everything is perfect.....

I'd have to know the circumstances. When you say several YT machines with new drives...are they JCI installed York drives or are they some off the shelf drive someone scabbed in? Reason I ask is that YTs haven't been produced since 2003 (I think). So new indicates to me these chillers have been retrofitted.

Yep, several chillers with TM2 removed and retrofitted with new vfd's. Tower water consistently around 65-68, but do run low load from time to time. Surge maps detecting surges but seem to be stalls more than surges.

And yes, they were installed by Johnson. Had them back out (warranty) when they wouldn't back off, they cleared the map. Ran for 2 days properly, loaded up map again, now at 60 hz all the time. Still putzing (professional term) around to try to smooth out operation.

The symptom you describe could be caused by electrical noise. There are grounding procedures that need to be followed to minimize noise. The ACC board was scheduled to be phased out. Are these Optiview or Spectrum panels? Do these installations have ACC boards?

I can't remember a time when I saw a chiller corrupt a surge map in two days. Generally it takes a week or more. I had a problem job like that one time. No matter what we did it seemed to corrupt the map. Luckily I had a good relationship with the guys at the factory and I got to do the beta testing for modbus communications on this chiller/VSD. Once the VSD logic board and microboard were changed, the map corruption problem went with it.

Another thing that will drive them nuts is if the controls aren't steady. If the BAS is changing the leaving chilled water setpoint too rapidly or speeding up or slowing down the pumps too rapidly they freak. Any chance this is a variable primary chilled water system?

I still believe the York VSD is the best on the market. No other manufacturer can seem to turn down like the York will.

I think you are confusing "stall" with surge. The tower problems would not contribute to the low load conditions of which you speak. The rumbling one experiences in low load conditions is usually not a surge, but rather a "stall" condition. The two are very different conditions. Surging occurs when actual head exceeds design head. A stall condition occurs when then refrigerant gas recirculates within the impeller and is unable to be pushed into the volute. After York came out with the YK series there were cases of stall that needed to be addressed. Stall can cause damage to the compressor/chiller as well. What York developed was the VGD or variable geometry diffuser. This diffuser closes the gap in the discharge wall to allow the refrigerant to get through the volute and into the condenser.

So york developed the movable diffuser?, one reliant on oil pressure or electronics?, just curious, who knows what banner they are flying under now, got a few pe (westinghouse), 1972 design still going.

So york developed the movable diffuser?, one reliant on oil pressure or electronics?

Yes, the VGD or variable geometry diffuser has been in production for quite a number of years (I'm going to guess around 8 years...could be more). It's controlled by a transducer in the discharge volute. It senses small pulsations in the discharge gas. The control scheme is involved. The end result is that the machines are much more stable over varying load conditions. JCI bought York in 2005. The York product is still made, but I have the feeling that JCI will eliminate the York brand name sometime in the future. The company is that arrogant, IMHO.